// Copyright (c) 2012 The Chromium Authors. All rights reserved.
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef NET_BASE_ADDRESS_TRACKER_LINUX_H_
#define NET_BASE_ADDRESS_TRACKER_LINUX_H_

#include <sys/socket.h> // Needed to include netlink.
// Mask superfluous definition of |struct net|. This is fixed in Linux 2.6.38.
#define net net_kernel
#include <linux/rtnetlink.h>
#undef net
#include <stddef.h>

#include <map>
#include <unordered_set>

#include "base/callback.h"
#include "base/compiler_specific.h"
#include "base/macros.h"
#include "base/message_loop/message_loop.h"
#include "base/synchronization/condition_variable.h"
#include "base/synchronization/lock.h"
#include "base/threading/thread_checker.h"
#include "net/base/ip_address.h"
#include "net/base/network_change_notifier.h"

namespace net {
namespace internal {

    // Keeps track of network interface addresses using rtnetlink. Used by
    // NetworkChangeNotifier to provide signals to registered IPAddressObservers.
    class NET_EXPORT_PRIVATE AddressTrackerLinux : public base::MessageLoopForIO::Watcher {
    public:
        typedef std::map<IPAddress, struct ifaddrmsg> AddressMap;

        // Non-tracking version constructor: it takes a snapshot of the
        // current system configuration. Once Init() returns, the
        // configuration is available through GetOnlineLinks() and
        // GetAddressMap().
        AddressTrackerLinux();

        // Tracking version constructor: it will run |address_callback| when
        // the AddressMap changes, |link_callback| when the list of online
        // links changes, and |tunnel_callback| when the list of online
        // tunnels changes.
        // |ignored_interfaces| is the list of interfaces to ignore.  Changes to an
        // ignored interface will not cause any callback to be run. An ignored
        // interface will not have entries in GetAddressMap() and GetOnlineLinks().
        // NOTE: Only ignore interfaces not used to connect to the internet. Adding
        // interfaces used to connect to the internet can cause critical network
        // changed signals to be lost allowing incorrect stale state to persist.
        AddressTrackerLinux(
            const base::Closure& address_callback,
            const base::Closure& link_callback,
            const base::Closure& tunnel_callback,
            const std::unordered_set<std::string>& ignored_interfaces);
        ~AddressTrackerLinux() override;

        // In tracking mode, it starts watching the system configuration for
        // changes. The current thread must have a MessageLoopForIO. In
        // non-tracking mode, once Init() returns, a snapshot of the system
        // configuration is available through GetOnlineLinks() and
        // GetAddressMap().
        void Init();

        AddressMap GetAddressMap() const;

        // Returns set of interface indicies for online interfaces.
        std::unordered_set<int> GetOnlineLinks() const;

        // Implementation of NetworkChangeNotifierLinux::GetCurrentConnectionType().
        // Safe to call from any thread, but will block until Init() has completed.
        NetworkChangeNotifier::ConnectionType GetCurrentConnectionType();

        // Returns the name for the interface with interface index |interface_index|.
        // |buf| should be a pointer to an array of size IFNAMSIZ. The returned
        // pointer will point to |buf|. This function acts like if_indextoname which
        // cannot be used as net/if.h cannot be mixed with linux/if.h. We'll stick
        // with exclusively talking to the kernel and not the C library.
        static char* GetInterfaceName(int interface_index, char* buf);

    private:
        friend class AddressTrackerLinuxTest;

        // In tracking mode, holds |lock| while alive. In non-tracking mode,
        // enforces single-threaded access.
        class AddressTrackerAutoLock {
        public:
            AddressTrackerAutoLock(const AddressTrackerLinux& tracker,
                base::Lock& lock);
            ~AddressTrackerAutoLock();

        private:
            const AddressTrackerLinux& tracker_;
            base::Lock& lock_;
            DISALLOW_COPY_AND_ASSIGN(AddressTrackerAutoLock);
        };

        // A function that returns the name of an interface given the interface index
        // in |interface_index|. |ifname| should be a buffer of size IFNAMSIZ. The
        // function should return a pointer to |ifname|.
        typedef char* (*GetInterfaceNameFunction)(int interface_index, char* ifname);

        // Sets |*address_changed| to indicate whether |address_map_| changed and
        // sets |*link_changed| to indicate if |online_links_| changed and sets
        // |*tunnel_changed| to indicate if |online_links_| changed with regards to a
        // tunnel interface while reading messages from |netlink_fd_|.
        void ReadMessages(bool* address_changed,
            bool* link_changed,
            bool* tunnel_changed);

        // Sets |*address_changed| to true if |address_map_| changed, sets
        // |*link_changed| to true if |online_links_| changed, sets |*tunnel_changed|
        // to true if |online_links_| changed with regards to a tunnel interface while
        // reading the message from |buffer|.
        void HandleMessage(char* buffer,
            size_t length,
            bool* address_changed,
            bool* link_changed,
            bool* tunnel_changed);

        // Call when some part of initialization failed; forces online and unblocks.
        void AbortAndForceOnline();

        // MessageLoopForIO::Watcher:
        void OnFileCanReadWithoutBlocking(int fd) override;
        void OnFileCanWriteWithoutBlocking(int /* fd */) override;

        // Close |netlink_fd_|
        void CloseSocket();

        // Does |interface_index| refer to a tunnel interface?
        bool IsTunnelInterface(int interface_index) const;

        // Is interface with index |interface_index| in list of ignored interfaces?
        bool IsInterfaceIgnored(int interface_index) const;

        // Updates current_connection_type_ based on the network list.
        void UpdateCurrentConnectionType();

        // Used by AddressTrackerLinuxTest, returns the number of threads waiting
        // for |connection_type_initialized_cv_|.
        int GetThreadsWaitingForConnectionTypeInitForTesting();

        // Gets the name of an interface given the interface index |interface_index|.
        // May return empty string if it fails but should not return NULL. This is
        // overridden by tests.
        GetInterfaceNameFunction get_interface_name_;

        base::Closure address_callback_;
        base::Closure link_callback_;
        base::Closure tunnel_callback_;

        int netlink_fd_;
        base::MessageLoopForIO::FileDescriptorWatcher watcher_;

        mutable base::Lock address_map_lock_;
        AddressMap address_map_;

        // Set of interface indices for links that are currently online.
        mutable base::Lock online_links_lock_;
        std::unordered_set<int> online_links_;

        // Set of interface names that should be ignored.
        const std::unordered_set<std::string> ignored_interfaces_;

        base::Lock connection_type_lock_;
        bool connection_type_initialized_;
        base::ConditionVariable connection_type_initialized_cv_;
        NetworkChangeNotifier::ConnectionType current_connection_type_;
        bool tracking_;
        int threads_waiting_for_connection_type_initialization_;

        // Used to verify single-threaded access in non-tracking mode.
        base::ThreadChecker thread_checker_;
    };

} // namespace internal
} // namespace net

#endif // NET_BASE_ADDRESS_TRACKER_LINUX_H_
